The present invention relates generally to sports racquets, such as racquetball racquets, tennis rackets, squash racquets and badminton racquets used for hitting a projectile such as a ball, and more particularly for string configurations on sports racquets for providing greater deflection of the string resulting in more power when hitting the projectile.
Sports racquets, such as racquet ball racquets and tennis racquets, have evolved with the objective of improving their strength or power to hit a projectile, such as a ball or other propellable object such as a shuttlecock. The harder and faster a ball is hit and moves, the more difficult it is for an opponent to return the ball by hitting the ball accurately (if at all) with their racquet.
Older, conventional racquets are strung horizontally and vertically in a uniform manner from frame edge to frame edge to form a generally rectangular grid or string bed. Referring to FIG. 1, known non-long string racquets have between 75% and 86% of the length of their string beds or hitting surfaces covered by cross strings. This length is measured from the interior surface of the upper end of the frame of the racquet to the lower most cross string along the longitudinal axis. The string bed length is measured as the distance from the interior surface of the upper end of the frame along the longitudinal axis to an interior surface of the next-encountered, lower frame member.
Certain known aluminum racquets indicated with an * on FIG. 1 have an open throat piece where strings are present. A projectile, however, cannot access this area of the these racquets and is not part of the hitting surface. Herein, the term string bed only refers to the hitting surface. These racquets are made with a frame member that begins with a substantially straight section, is curved outwardly and around the string bed, and terminates in a substantially straight section that is disposed close to or substantially parallel to the beginning straight section. The two straight sections (which are also used to form the racquet handle or shaft) are so close together that a projectile cannot get between them. For these racquets, the length of the hitting surface is given as the length along the longitudinal axis of the racquet from the inner surface of the top frame member to the point at which the beginning and ending racquet frame sections are no more than 0.25 inches apart. For tennis rackets, the frame sections are typically about 0.7 inches apart.
Cross strings are provided on the known racquets to brace the main strings laterally so that the impact of the ball on the strings does not push the main strings aside. This would cause a loss of energy while hitting the ball by causing motion of the strings in a direction parallel to the face of the racquet or string bed rather than perpendicular to the string bed as desired to transfer that energy to the ball.
In addition, when a ball is permitted to travel too far through the string bed by pushing the main strings aside, the trajectory of the ball from the string bed will be adversely affected, making it more difficult to control the direction of the ball.
Also for known strings that are used on racquets, the cross strings also help to absorb the impact forces reducing the force on any one string, which further reduces string breaks. Finally, cross strings may act to dampen vibration.
Cross strings on the string bed, however, constrain deflective movement of the main strings in a direction normal or perpendicular to the string bed. It has been found that the greater the deflection of the string, the greater the xe2x80x9cdwellxe2x80x9d time with the ball, which stores greater energy. This in turn causes a ball to be propelled from a racquet with more power and speed.
Instead of eliminating cross strings to gain this power, one improvement lengthens the strings instead. This is disclosed, for example, in U.S. Pat. No. 5,919,104 issued to Mortvedt et al., and which is entirely incorporated herein by reference. The ""104 patent discloses that the vertical or main strings can be lengthened by wrapping an end of the strings around a pin inside the distal or far end of the handle. Thus, even though the string bed in such a racquet is about 15.5 inches long, the effective length of the main or xe2x80x9clongxe2x80x9d strings extending into the handle is about 22 inches. For tennis rackets, the effective lengths for long strings are about 27 to 28 inches.
It can be seen from the known racquets that eliminating any major number of extra strings was simply not considered a realistic option. Thus, removing all cross strings has never been considered at all.
The problems mentioned above are solved by the invention, which in a first aspect provides a racquet for hitting a projectile, and that has a handle and a racquet head with a frame extending from the handle. It also supports a tensioned string bed. The frame has an upper portion on an opposing end of the frame relative to the handle and a longitudinal axis extending from the upper portion to the handle. The string bed includes main strings generally running parallel to the longitudinal axis and cross strings running generally perpendicular to the longitudinal axis. The string bed has an upper end defined at an interior surface of the upper portion and a lower end disposed at an interior surface of a lower end of the frame near the handle. A length is defined from the upper end to the lower end of the string bed. The cross strings are only disposed at most within approximately an upper 70% of the length of the string bed, and more preferably 68% or 65%, and most preferably at 60%.
In another aspect of the present invention, a racquet for hitting a propellable object, has a racquet head with a frame. The frame has an upper portion at one end and a handle at an opposing end to the upper portion. A tensioned string bed is disposed on the frame and has main strings and cross strings. The string bed defines a longitudinal central axis from the upper portion to the handle end of the frame. The string bed has a length along the axis of at least 15.5 inches, while the string bed has at most 19 cross strings total.
In yet another aspect of the invention, a sports racquet for hitting a projectile has a hollow stem that defines a cavity. A racquet head is attached to the stem and has a frame extending from the handle and supports a tensioned string bed. The frame has an upper portion on an opposing end of the frame relative to the stem. A longitudinal axis extends from the upper portion to the stem, which is either a handle or a shaft attaching a handle to the frame. The string bed includes main long strings generally running parallel to the longitudinal axis. The main long strings extend into the cavity of the stem. Cross strings run generally perpendicular to the longitudinal axis. The string bed has an upper end defined at an interior surface of the upper portion and a lower end disposed at an interior surface of a lower end of the frame near the handle, and a length parallel to the longitudinal axis from the upper end to the lower end of the string bed. The cross strings are only disposed at most within approximately an upper 70% of the length of the string bed measured from the upper end, and more preferably 68% or 65%, and most preferably at 60%.
In yet a further aspect of the invention, a racquet for hitting a propellable object, has a racquet head with a frame. The frame has an upper portion at one end and a hollow stem at an opposing end to the upper portion. The stem defines a cavity and is either a handle or a shaft attaching a handle to the frame. A tensioned string bed is disposed on the frame and has main long strings extending into the cavity. Cross strings are also provided. The string bed defines a longitudinal central axis from the upper portion to the handle end of the frame. The string bed has a maximum length along the axis of about 15.5 inches, while the string bed has at most 19 cross strings total.
The invention also includes a method of stringing a racquet with a frame that has holes for holding a string bed. The frame and string bed have a defined number of main strings and a defined number of cross strings. The method includes the steps of stringing a string in and out of holes on the frame for forming the string bed, and intentionally stopping the stringing before using all holes on the frame provided for the defined number of cross strings. This forms a number of cross strings that is less than the defined number of cross strings to increase deflection of the string bed.